1. Field of the Invention
The present invention relates to a filter plug feeding apparatus for manufacturing filter plugs for cigarettes, and in particular, to a grading device for separating components or elements of filter plugs coaxially arranged, from one another in their feeding direction during the filter plug manufacturing process.
2. Description of the Related Art
A typical example of a filter cigarette manufacturing machine or a so-called filter attachment is disclosed in U.S. Pat. No. 4,867,734. This conventional filter attachment is provided with a filter plug feeding apparatus, which forms dual filter plugs, and feeds the formed filter plugs to grooved drums which constitute a transportation path of the filter attachment. The transportation path is used to transport pairs of cigarettes in the filter attachment.
More specifically, the feeding apparatus comprises a pair of hoppers, which are stored individually with charcoal filter rods and plain filter rods. The charcoal and plain filter rods delivered from the pair of hoppers are transferred toward the transportation path. In this process of transfer, various operations, such as cutting, separation, joining, grading, orientation, etc., are carried out. At the end of the transfer process, dual filter plugs are formed each having one plain plug and a pair of charcoal tips situated individually on the opposite sides thereof. Each dual filter plug formed in this manner is fed to the transportation path, and is located between a pair of cigarettes on this transportation path. Plain plugs and charcoal tips are obtained by cutting plain filter rods and charcoal filter rods, respectively.
In the filter attachment, thereafter, the pair of cigarettes and the dual filter plug are connected to one another by means of a tip paper piece, whereupon a double filter cigarette which is equivalent to two filter cigarettes is formed. The double filter cigarette is cut into two equal parts or filter cigarettes.
The formation of the dual filter plug mentioned before will be described below in detail. The charcoal filter rod is cut into a pair of charcoal half rods. These charcoal half rods are separated from each other in their axial direction. On the other hand, the plain filter rod is supplied between the pair of charcoal half rods, and is situated coaxially with these charcoal half rods.
The paired charcoal half rods and the plain filter rod are individually cut into equal parts to obtain a pair of charcoal groups and one plain group. Elements in the respective groups are plural charcoal chips or plain plugs, which are coaxially situated.
The aforesaid dual filter plug is formed by combining charcoal chips taken out one by one from individual charcoal groups and one plain plug taken out from the plain group.
In order to form a dual filter plug, during a process of feeding charcoal and plain groups, it is required to separate elements of each group from each other in their feeding direction, that is, to perform grading so that only a paired charcoal and one plain plug are coaxially situated.
For this reason, a device for separating elements in each group from each other in the feeding direction, that is, a grading device, is incorporated into the known filter plug supply apparatus described before. The grading device includes means for successively catching elements in each group in order to temporarily stop the feeding of the elements or means for decreasing or increasing the feeding speed of the elements in the group. Thus, the group elements can be separated from each other in the feeding direction.
However, in the grading manner described above, excessive force is applied to these elements because the feeding speed of individual elements is suddenly varied. For this reason, an impression occurs on the outer peripheral surface of these elements, that is, charcoal chips and plain plugs, or chips or plugs are collapsed, causing deformation. In particular, in the case where charcoal chips and plain plugs are obtained by cutting a neo-filter rod made of a pulp fiber, restoring ability of these chips and plugs is low; therefore, the above-mentioned impression or deformation is easy to leave therein. Such an impression or deformation influences formation and feeding of dual filter plugs in the next stages, and causes a disadvantage that the supply of dual filter plugs to the aforesaid transportation path becomes impossible, or wrapping of chip paper piece in the filter attachment is defective.